The UK’s fifth carbon budget calls for a 57% reduction in greenhouse gas (GHG) emissions relative to 1990 levels by 2028-2032. This post evaluates whether this goal is achievable and concludes that at best it will be difficult to meet. It also reviews the reasons behind the UK’s apparent success in reducing its GHG emissions (down by 36% in 2014 relative to 1990) and concludes that this reduction is largely a result of market forces and that renewable energy has played only a minor part. The post also highlights the fact that only about a quarter of UK GHG emissions come from the electricity sector, meaning that the UK’s emissions targets can be met only by making major reductions in emissions from the other energy-consuming sectors, which is a much tougher proposition.
The data used in the post are from the Committee on Climate Change’s Fifth Carbon Budget report , the Climate Change Committee’s Central Scenario data, the DECC Greenhouse Gas Emissions National Statistics or the Climate Change Committee’s Excel spreadheets unless otherwise specified.
The UK’s carbon budget is set by the Climate Change Committee (CCC), “an independent statutory body which was established under the Climate Change Act (2008) to advise UK and devolved administration governments on setting and meeting carbon budgets, and preparing for climate change.” The CCC’s fifth carbon budget has now been adopted by Parliament, and a projection of historic trends makes it look as if it will be achievable:
Figure 1: Emissions trends relative to carbon budgets and the “80% by 2050” target (reproduced from the CCC Report)
There are, however, two reasons to suppose it may not be. The first is that much of the low-hanging fruit has already been picked, which will make it progressively more difficult to keep the trend line heading down. The CCC recognizes as much when it says:
Our proposed budget requires a continuation of the increase in take-up of ultra-low emission vehicles (e.g. electric and plug-in hybrid cars and vans) and low-carbon heat (e.g. heat networks and heat pumps) required by the fourth carbon budget. These changes will require bigger behavioural adjustments than emissions reductions to date, but are needed to prepare for the 2050 target. To involve genuine emissions reductions they should be accompanied by deep reductions in emissions from electricity generation. It is important to signal this direction in advance given the time required to develop new policies, to grow currently nascent markets, for consumer behaviours to adapt and to invest in supporting infrastructure and innovation.
How much success will be achieved in getting consumers to adapt their behavior is questionable. And how are the “deep reductions in emissions from electricity generation” to be achieved? According to the CCC:
This reduction could be delivered by a range of different mixes of low-carbon generation (i.e. renewables, nuclear and CCS), reaching a total share of around 75% of generation by 2030. It is important that the low-carbon portfolio includes roll-out in the 2020s of offshore wind and CCS given their long-term importance and the role of UK deployment in driving down costs.
Figure 2 shows the CCC’s “central scenario” future generation mix, which will achieve the desired emissions reduction. Coal disappears, gas and nuclear generation decrease and the difference is made up with a variety of renewable sources in which wind plays the leading role. But whether wind capacity can be expanded this much given the dwindling level of renewables investment in Europe and the as-yet-unknown impacts of Brexit is uncertain. Second comes CCS, which can already be discounted as a failed technology. There is also a growing realization that biomass is not a carbon-free fuel even though the CCC treats it as such. How much biomass will figure in the UK’s 2030 generation mix is therefore also open to question. It’s easy to see how this generation mix could fall 100TWh or more short of meeting projected 2030 annual electricity demand.
Figure 2: The CCC’s “Central Scenario” generation mix. Data from the CCC’s Central Scenario spreadsheets.
The second reason relates to historic trends. Figure 3 shows UK annual CO2 emissions from all sources – not just the electricity sector – since 1970. Note that other greenhouse gases such as methane and nitrous oxide are not included.
Figure 3: UK total GHG emissions since 1970 expressed as CO2 equivalent: Data from CCC spreadsheets.
The UK’s CO2 emissions have been generally decreasing since at least 1970, and this long-term decrease clearly has nothing to do with renewables . As shown in Figure 3 it was largely a result of decreases in coal and petroleum consumption and an increase in the consumption of North Sea gas from 1970 through 2000, with emissions flattening between 2000 and 2007 as gas consumption leveled off:
Figure 4: UK total GHG emissions by source since 1970. Data from CCC spreadsheets.
The key question, however, is why CO2 emissions began to decrease more rapidly after 2007. The two main factors that could have contributed to this decrease are:
- Decreased demand caused by the 2008/9 recession
- Renewables growth
Between 2007 and 2014 the percentage of renewables in the UK electricity generation mix increased by 7%, which assuming no significant changes in the generation mix would have produced a 7% decrease in CO2 emissions from electricity generation. But according to the CCC electricity sector emissions account for only about a quarter of UK total emissions, so the overall impact of renewables on total UK emissions would have been less than 2%. We can therefore conclude that the accelerated emissions decrease since 2007 is mostly a result of the 2008/9 recession, with the implication being that emissions will decrease a lot less rapidly when and if the UK finally pulls out of it.
The important point, however, is that electricity sector emissions account for only about a quarter of total UK emissions. Reducing emissions from the sectors that produce the remaining three-quarters will therefore have three times the impact of electricity sector reductions – a fact we tend to forget . Figure 5 illustrates the emissions reductions needed to meet the fifth carbon budget target. Reductions in electricity sector emissions are larger percentage-wise than in the other sectors but the other sectors still account for 65% of the total reduction:
Figure 5: Emissions reductions by sector needed to reach the fifth carbon budget target. Reproduced from the CCC report.
And how does the CCC plan to achieve the reductions in the non-electric sectors? It doesn’t. Reducing emissions from millions of cars, buses, trains, water heaters, heat pumps, businesses, factories, waste dumps, farms and houses is a vastly more complicated undertaking than reducing emissions from a couple of hundred power plants, and it can’t be planned in any detail. So the CCC resorts to assumptions, chief among which are:
Industry: improved energy management and process control, use of more energy-efficient plant and equipment, waste heat recovery, use of bioenergy in space and process heat, and development of a carbon capture and storage (CCS) cluster allowing use of CCS in the iron and steel and chemicals sectors. Hydrogen could provide an alternative to CCS depending how technologies develop.
Buildings: deployment of low-carbon heat increases so that heat pumps and heat networks from low-carbon sources provide heat for around 13% of homes and over half of business demand; insulation increases (including a further around 1.5 million solid walls and 2 million cavity walls in the 2020s), and there is more use of heating controls and efficient lights and appliances. Alternatively, low-carbon heat could be provided via hydrogen added to the gas grid or using hybrid heat pumps, which include a gas boiler to top-up heat supply on the coldest days.
Transport: efficiency of conventional vehicles continues to improve in the 2020s (e.g. conventional car emissions fall from 125 gCO2/km in 2014 to 102g/km in 2020 then 86g/km in 2030 …. the combination of plug-in hybrids and battery electric vehicles reach 9% of new car and van sales in 2020 and around 60% in 2030). We include hydrogen buses (reaching 25% of sales in 2030), with the possibility of a bigger contribution from hydrogen for other vehicles types.
Are these changes achievable? There’s no way of knowing. But CCS is out, and where is the hydrogen to come from? And will market forces alone cause people to buy more low-carbon vehicles, install more energy efficient plants and insulate their homes? As noted in the first quote, the CCC thinks they won’t. We will need changes in consumer behavior, “new policies” and “growth in nascent markets”.
These changes will require bigger behavioural adjustments than emissions reductions to date, but are needed to prepare for the 2050 target ….. It is important to signal this direction in advance given the time required to develop new policies, to grow currently nascent markets, for consumer behaviours to adapt and to invest in supporting infrastructure and innovation.
And consumer resistance to changing consumer behavior being what it is, these changes will presumably have to be enforced through even higher energy prices and/or yet more subsidies.
A final issue is the impact of other greenhouse gases such as methane and nitrous oxide, which are included in the UK’s official tabulations as CO2 equivalents. Figure 6 shows total UK greenhouse gas emissions when these GHGs are added. They make an appreciable difference:
Figure 6: Total UK emissions segregated by the type of greenhouse gas and expressed as CO2 equivalents. Data from CCC spreadsheets.
The non-CO2 GHGs also show decreasing trends in total emissions since 1990, and these trends amplify the decrease in total UK emissions after conversion to CO2 equivalent values. But only methane has made a significant contribution to total emissions, so we will concentrate on that.
There are, however, problems with methane data sources. The DEFRA data, for example, show substantially the same methane emissions levels as Figure 6 after multiplying methane by 25 to convert it to a CO2 equivalent, but it shows “energy-transport” as the dominant methane source. All other data sources show emissions from waste dumps and agriculture as the dominant methane sources:
Figure 7: DEFRA’s version of the sources of UK methane emissions
Not knowing quite what to do about this I went to the DECC data, which although they show ~30% lower methane emissions than Figure 5 and end in 2010 rather than 2013 at least have the methane sources correctly categorized:
Figure 8: DECC’s version of the sources of UK methane emissions
According to Figure 8 the decline in methane emissions since 1990 has been caused by declining energy supply emissions – a result of decreasing coal usage – and declining waste management emissions, reportedly caused by improvements in the way waste is managed. But agricultural emissions have remained more or less the same and total emissions are slowly converging on them, suggesting that there isn’t much more squeal to be got out of this particular pig. And as shown in Figure 9, DECC projects only minor decreases in future methane emissions. It seems that the UK is not going to get much help from methane in meeting its long-term emissions goals.
Figure 9: Actual and projected methane emissions. Data from DECC.
Time to sum up. To meet the fifth carbon budget the UK must, by 2030:
1. Reduce electricity sector emissions by approximately 70%, representing 35% of the total emissions reduction.
2. Reduce emissions from other energy-consuming sectors by approximately 30%, representing 65% of the total emissions reduction.
The CCC has developed a 2030 generation mix that reduces electricity sector emissions by the desired amount, but it includes CCS and some other questionable items, so there are doubts as to whether it will deliver the desired results.
The CCC has no plan for reducing other sector emissions, basing its estimates entirely on unverified (and unverifiable) assumptions regarding the percentage of EVs, insulated homes etc. that may exist 14 years from now. There are no guarantees that these percentages will be achieved, and the CCC acknowledges that achieving them will be difficult. As the CCC puts it: Meeting the fifth carbon budget will require progress in increasingly difficult areas to continue reducing emissions.
Overall it doesn’t look good.